Enfermedad del gusano de Guinea

Dracunculiasis (Guinea worm disease) is caused by the nematode (roundworm) Dracunculus medinensis.¹ During the last 25 years, efforts to eradicate the Guinea worm have resulted in a reduction of more than 99% of worldwide cases of dracunculiasis.

Life cycle of dracunculiasis²

Drinking unfiltered water containing copepods, small crustaceans infected with D. medinensis larvae, causes humans to become infected in 2 ways:

• After consumption, the copepods die and release the larvae, which enter the stomach and intestinal wall of the host and enter the abdominal cavity and retroperitoneal space.

• After maturation into adults and copulation, the male worms die and the females (length 70–120 cm) migrate in the subcutaneous tissues.

About a year after infection, the female worm causes a skin blister to form and burst, usually on the distal lower extremities. The female worm emerges and releases larvae when this lesion comes into contact with water, which the patient seeks out to soothe the area’s agony.

A copepod ingests the larvae and the cycle is completed when the copepods are consumed.

How common is dracunculiasis? (Epidemiology)³

The disease is typical of rural communities in low-income countries, whose survival depends on the presence of open surface water. Therefore, disease prevalence highly depends on rain patterns and climate:⁴

• In arid areas, transmission occurs mainly in the rainy season, when surface water is more easily available.

• In wet areas, the disease strikes more intensely in the dry season, when drinking water sources are few, as stagnant water collection points, such as wells and cisterns, are well-known parasite reservoirs.

During the mid-1980s an estimated 3.5 million cases of dracunculiasis occurred in 20 countries worldwide, 17 countries of which were in Africa and the 3 others in Asia.

The number of reported cases fell to fewer than 10,000 cases for the first time in 2007, dropping further to 542 cases in 2012. Since 2015, human cases have stayed at double digits (54 in 2019 and 27 human cases in 2020). These human cases were reported from Angola (1), Chad (12), Ethiopia (11), Mali (1), South Sudan (1) and Cameroon (1) – likely imported from Chad.

Dracunculiasis symptoms (presentation)²

Most Guinea worm patients do not exhibit any symptoms for about a year following their initial infection. People do not begin to feel ill until the worm is about to burst through the skin.

Symptoms include fever, nausea, vomiting, diarrhoea, shortness of breath, burning, itching, discomfort, and swelling where the worm is in the body (typically the legs and feet), and blisters when the worm breaks through the skin.

Investigaciones¹

• The clinical presentation is so typical that it does not need laboratory confirmation.

• Examination of the fluid discharged by the worm may show rhabditiform larvae.

• FBC: the white cell count is usually slightly elevated with an eosinophilia.

• There are no serological tests available.

• X-rays of the lower limbs may show calcified worms.

Dracunculiasis treatment²

• The most common treatment still involves wrapping the worm around a stick at the skin surface, and wrapping or winding the worm a few centimetres each day.
  

  • This process can take up to eight weeks, but must be slow to avoid breakage and leaving behind a portion of the worm.

  • Leaving a portion of the dead worm within the host's body increases the risk of infection, and can trigger immune responses, resulting in pain and swelling.

  • Wading can contaminate the water and spread the infection and so should be avoided until the worm is completely removed.

• The worm also can be excised surgically.

• Local cleaning of the lesion, and applying a topical antibiotic for any bacterial superinfection.

• Pain and swelling can be reduced with the aid of anti-inflammatory medications.

• There is no appropriate or curative antihelminthic medication.

Pronóstico²

Prognosis is usually good with or without treatment, unless any secondary infection remains untreated. However, although guinea worm sickness only very occasionally results in death, it can cause permanently disability.

Without proper care, worm-related wounds can develop bacterial infections that result in sepsis, septic arthritis, and contractures.

Dracunculiasis prevention³

• Drink only water from underground sources free from contamination, eg, borehole or hand-dug wells.

• Prevent persons with an open Guinea worm ulcer from entering ponds and wells used for drinking water.

• Always filter drinking water, eg, cloth or nylon mesh filter.

• Additionally, unsafe sources of drinking water can be treated with an approved larvicide.